The crosssectionof the passage is a regular or irregular plane polygon, and then the specific surface area is large and the mass transfer efficiency is high.
通道横截面为规则或不规则平面多边形，因而比表面积大、传质效率高。
2
The riverbed form in different periods from 1958 to 2005 of the South Channel and the South-North-Passage bifurcation and the cross-section transformation between U-shape and W-shape are analyzed.